The night before the class excursion to Kamakura, Koguma comes down with a fever, and must cancel. The next morning, after her fever is gone, she makes the bold decision to hop on her Cub and set out on the long journey to catch up to her class.

After a snowy night during winter vacation, Reiko invites Koguma over to her house for a surprise. The pair equip their Cubs for the snow, and enjoy a day of fun outside. Shii's father reveals how much of an influence the girls are having on Shii.

Koguma rushes to the narrow dirt road on her Cub to find Shii, who is half-submerged in a freezing river. She takes her back to her apartment to warm her up and dry her out, but Shii soon reveals that she has other, deeper issues with the winter weather.

The girls pack up and depart on a road trip to Kyushu, the most distant location their Cubs will take them, in order to shake off their winter doldrums and embrace spring. Along the way, Shii finds what she needs to help her continue her café project.